Electromagnetic signal processing devices, especially those operating in the microwave range, are widely used in industry today and are especially prevalent in the fields of radar, communications, and electronic warfare systems. Existing devices include oscillators, amplifiers, switches, modulators, demodulators, and non-linear transmission lines, among others.
One prior art system which may be relevant to the present invention is the radial disc resonator oscillator/amplifier of U.S. Pat. No. 4,600,894 as issued to Dydyk. The Dydyk system comprises a substrate having a hole extending therethrough, a radial disc resonator disposed on one face of the substrate such that it covers the hole, a microstrip conductor with a predetermined width disposed on the same face as the radial disc resonator, and a negative impedance device disposed below the hole on the side of the substrate opposite that of the radial disc. This system is designed to offer two degrees of freedom so that the external quality factor as well as the output coupling coefficient is selectable.
The Dydyk system has several drawbacks, however. Due to the nature of its structure, the Dydyk invention is very difficult to fabricate monolithically; thus, it is expensive to produce in large quantities. Another drawback is that each individual structure performs one and only one discrete function. If a plurality of functions should be desired, a plurality of structures would be needed. This is economically infeasible as well as space-inefficient.
Another relevant signal processing device is a linear structure microwave amplifier that receives input microwave signals at one end and amplifies the signals as they propagate to the other end. Because this structure extends in only one dimension, it is relatively long, hence, requiring more space than would be preferable. The linear structure also suffers from end effects and has difficulty in providing a good matching impedance for incoming electromagnetic signals. This causes portions of the input signals to be reflected, resulting in a partial loss of the input signal.